Insect repellent

ABSTRACT

The invention relates to an insect repellent which contains at least one fatty acid alkyl ester having 1 to 4 carbon atoms in the alkyl group and at least one natural, nature-identical or synthetic fatty alcohol as the active substance and at least one natural or nature-identical vegetal or animal fatty oil as the carrier. The insect repellent serves for repelling flying, biting and sucking insects in man and beast and is applied onto the skin.

The present invention relates to an insect repellent against flying,biting and sucking insects.

Repellents are chemical substances having a repellent effect on insects.Their use in human and veterinary hygiene is of great practicalimportance, where they protect man and beast against attack bybloodsucking, biting or otherwise annoying insects. It is required thatrepellents which are directly applied onto the skin are well toleratedby the skin, non-toxic, perspiration-resistant and light-fast andperfect in cosmetic respect. Moreover, the protection of the treatedskin areas is to last for the longest possible period of time and thespectrum of activity of the repellents is to be as broad as possible,i.e. they should act against the largest possible number of harmful andannoying insects.

In the past, essential oils such as citronella oil, camphor andeucalyptus oil have been used as repellents; however, due to theirdisadvantages they were predominantly replaced by synthetic repellents.Synthetic repellents used in the prior art are e.g. phthalic aciddimethyl ester, 1,2-ethyl hexane-1,3-diol,3,4-dihydro-2,2-dimethyl-4-oxo-2H-pyran-6-carboxylic acid-n-butyl ester,succinic acid dipropyl ester, N,N-diethyl-3-methyl-benzoic acid amideand pyridine-2,5-dicarboxylic acid-d-n-propyl ester (Ullmanns Encyklopadie der technischen Chemie, 4th edition, vol. 13, pages 237 et seq.,1977). However, such synthetic repellents are often notperspiration-resistant and irritate the mucous membranes. Skin toleranceand, more recently, also bio-degradability of each synthetic repellentmust at first be examined.

Accordingly, the present invention is based on the object of providingan effective repellent for application onto the skin on the basis ofnatural and nature-identical raw materials with the least toxicologicalrisk, which also develops a high effectiveness over a long period oftime.

According to the invention, this object is attained by a repellent whichcontains at least one fatty acid alkyl ester having 1 to 4 carbon atomsin the alkyl group and at least one natural, nature-identical orsynthetic fatty alcohol as the active substance and at least one naturalor nature-identical vegetable or animal fatty oil as the carrier.

Moreover, the present invention relates to the use of the repellentaccording to the invention for repelling flying, biting and suckinginsects in man and beast.

Examples for the fatty acid alkyl esters having 1 to 4 carbon atoms inthe alkyl group, which are used in the insect repellent according to theinvention are methyl, ethyl or butyl esters of fatty acids from naturalor nature-identical vegetal or animal fatty oils from the groupconsisting of rape-seed oil, sunflower oil, peanut oil, peanut butter,soy oil, safflower seed oil, cuphea oil, coconut oil, palm kernel oil,palm oil and fish oil. Fatty acids having 5 to 19 carbon atoms arepreferred.

A natural, nature-identical or synthetic fatty alcohol having preferably5 to 18 carbon atoms, being saturated or having 1 to 3 unsaturated bondsper molecule is admixed to the used fatty acid alkyl ester as a furtheractive substance according to the invention. The natural fatty alcoholsare e.g. obtained from vegetal and/or animal oils and/or the fatty acidsand/or fatty acid alkyl esters, which can be obtained therefrom. Thenature-identical and/or synthetic fatty alcohols can e.g. be obtainedfrom paraffin and/or ethene. A preferred active substance combination ofthe repellent according to the invention contains 1 to 99% by weight ofthe fatty acid alkyl ester and 99 to 1% by weight of the fatty alcohol.

In further preferred embodiments, the repellent according to theinvention contains 70 to 98% by weight of fatty acid alkyl ester and 30to 2% by weight of fatty alcohol, 30 to 2% by weight of fatty acid alkylester and 70 to 98% by weight of fatty alcohol, 60 to 97% by weight offatty acid alkyl ester and 40 to 3% by weight of fatty alcohol or 40 to3% by weight of fatty acid alkyl ester and 60 to 97% by weight of fattyalcohol.

In order to slow down the evaporation of the active substance(s) and toachieve the effect over an especially long period of time due to this,at least one carrier from the group consisting of natural ornature-identical vegetal or animal fatty oils is added to the repellentaccording to the invention. Examples of the natural or nature-identicalvegetal or animal fatty oils are rape-seed oil, sunflower oil, peanutoil, peanut butter, soy oil, safflower seed oil, cuphea oil, coconutoil, palm kernel oil, palm oil and fish oil.

At least one free fatty acid may be contained in the repellent accordingto the invention as an additional carrier. These are e.g. obtained bymeans of the hydrolytic decomposition of natural or nature-identicalvegetal and/or animal oils and have preferably 5 to 19 carbon atoms inthe chain. Examples are valeric acid, caproic acid, oenanthic acid,caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauricacid, tridecanoic acid, myristic acid, pentadecanoic acid, palmiticacid, margaric acid, stearic acid and nonadecanoic acid and isovalericacid, palmitoleic acid, oleic acid, sorbic acid, linolic acid, linolenicacid and elaeostearic acid.

An insect repellent containing 75 to 98% by weight of the fatty acidalkyl ester and 2 to 25% by weight of the fatty oil is also preferred.Moreover, an insect repellent is preferred, which contains 8 to 70% byweight of the fatty acid alkyl ester, 5 to 90% by weight of the fattyalcohol and 2 to 25% by weight of the fatty oil A further preferredinsect repellent contains 75 to 98% by weight of the fatty acid alkylester and 25 to 2% by weight of the free fatty acid or 1 to 97% byweight of the fatty acid alkyl ester, 1 to 97% by weight of the fattyalcohol and 2 to 25% by weight of the free fatty acid. Moreover, apreferred insect repellent comprises 1 to 96% by weight of the fattyacid alkyl ester, 2 to 25% by weight of the fatty oil and 2 to 25% byweight of the free fatty acid or 1 to 95% by weight of the fatty acidalkyl ester, 1 to 95% by weight of the fatty alcohol and respectively 2to 25% by weight of the fatty oil or the free fatty acid. Rape seed oilis preferred as natural vegetal oil, which may e.g. be contained in anamount of 20% to 80% by weight of a first runnings coconut methyl esterin the insect repellent.

The fatty alcohols, fatty acid alkyl esters and fatty acids may beobtained by means of a simple chemical reaction from natural ornature-identical, toxicologically harmless raw materials, e.g. by meansof hydrolysis, reesterification, hydrogenation, high-pressurehydrogenation, hardening and/or dehydration as known in the prior art.The fatty oils used according to the invention may also be obtained bymeans of conventional processes from oil-supplying materials such asplant seeds and animal fats. Accordingly, the insect repellent accordingto the invention contains one or several substances prepared fromcompletely harmless, synthetic (nature-identical) basic substances ordirectly from natural basic substances, and, consequently, has the leasttoxicological and irritative risk with an excellent repelling effect. Itis preferably used by applying it onto the skin of man and beast torepel flying, biting and sucking insects.

The following examples explain the invention.

1. Examples of insect repellents

(I) 20% by weight of rape seed oil 20% by weight of coconut methyl ether(8 to 18 carbon atoms in the fatty acid radical) 50% by weight of firstrunnings coconut fatty alcohol (C₈ to C₁₀)

(II) 10% by weight of rape seed oil 10% by weight of first runningscoconut palm kernel fatty acid (C₈ to C₁₂) 35% by weight of coconutmethyl ester (8 to 18 atoms in the fatty acid radical) 45% by weight offirst runnings coconut fatty alcohol (C₈ to C₁₀)

(III) 30% by weight of rape seed methyl ester 5% by weight of soy methylester 10% by weight of sunflower methyl ester 5% by weight of coconutmethyl ester 30% by weight of first runnings coconut methyl ester 15% byweight of first runnings palm kernel alcohol 5% by weight of rape seedoil

2. Application Examples

The insect repellents (I) and (II) were tested with two differentpersons.

Test:

The forearm of a test subject was treated with the corresponding testsubstances (I) or (II) on an area of approx. 250 cm². The amount of 2 mlof the corresponding test substance was distributed uniformly. Thetreated forearm area was sealed at both ends with a mosquito-tightadhesive tape and a short plastic hose. The untreated hand was coveredby a thick glove and, thus, served at the same time as a control for thebiting activity of the test animals.

About 300 to 400 yellow fever mosquitoes (Aedes aegypti), almostexclusively females, were placed into a breeding cage measuring 40×40×40cm.

The forearm and the hand were held into the mosquito cage for the testevery hour, and, for 10 minutes, the number of mosquitos was recorded,which

(a) attempted to bite through the glove (positive control),

(b) approached the treated area closer than 3 cm,

(c) remained seated on the treated area longer than 2 seconds, and

(d) bit the treated area and sucked blood.

Test substance (I) (Test subject (1))

    ______________________________________                                                                     Remaining                                                Glove   Approaching  seated  Biting                                   Time (h)                                                                              a)      b)           c)      d)                                       ______________________________________                                        1.5     100     33           14      0                                        2.5     100     27           12      0                                        4.0     100     45           37      0                                        5.0     100     26           5       0                                        6.5     100     46           30      0                                        ______________________________________                                    

Test substance (II) (Test subject (2))

    ______________________________________                                                                     Remaining                                                Glove   Approaching  seated  Biting                                   Time (h)                                                                              a)      b)           c)      d)                                       ______________________________________                                        1       160     51           17      0                                        2       130     50           27      0                                        3       100     50           5       0                                        4       100     --           17      0                                        5       100     24           13      0                                        6       100     63           36      0                                        7       100     99           62      0                                        ______________________________________                                    

The parameters a) and b) are estimated values since an exactdetermination is not possible.

The effectiveness of a substances results above all from the ratio ofthe mosquitoes, which are ready to bite and remain seated on the glove.The number of the biting mosquitoes is the decisive factor for theduration of the effect and, thus, in the tropics, indirectly also forthe risk of infection. The tested substances ensure protection of morethan 3 hours. As can be seen from the parameters b) and c) there is alsoa specific number of approaching mosquitoes and mosquitoes remainingseated if the substances according to the invention are used, however,they do not bite. Accordingly, a strong repellent effect can beattributed to all tested substances.

I claim:
 1. An insect repellant consisting essentially of (a) an activesubstance combination of 1 to 99% by weight of at least one fatty acidalkyl ester having 1 to 4 carbon atoms in the alkyl group and 99 to 1%by weight of at least one natural, nature-identical or synthetic fattyalcohol having 5 to 18 carbon atoms in (b) a carrier of at least onenatural or nature-identical normally liquid vegetal fatty oil selectedfrom the group consisting of rape-seed oil, sunflower oil, peanut oil,soy oil, and coconut oil.
 2. An insect repellant according to claim 1,wherein the repellant contains 75 to 98% by weight of the fatty acidalkyl ester and 2 to 25% by weight of the fatty oil.
 3. An insectrepellant according to claim 1, wherein the repellant contains 8 to 80%of the fatty acid alkyl ester, 5 to 90% by weight of the fatty alcoholand 2 to 25% by weight of the fatty oil.
 4. An insect repellantaccording to claim 1, wherein the carrier also contains at least onefree fatty acid.
 5. An insect repellant according to claim 4, whereinthe repellant contains 75 to 98% by weight of the fatty acid alkyl esterand 25 to 2% by weight of the free fatty acid.
 6. An insect repellantaccording to claim 4, wherein the repellant contains 1 to 97% by weightof the fatty acid alkyl ester, 1 to 97% by weight of the fatty alcoholand 2 to 25% by weight of the free fatty acid.
 7. An insect repellantaccording to claim 4, wherein the repellant contains 1 to 96% by weightof the fatty acid alkyl ester, 2 to 25% by weight of the fatty oil and 2to 25% by weight of the free fatty acid.
 8. An insect repellantaccording to claim 4, wherein the repellant contains 1 to 95% by weightof the fatty acid alkyl ester, 1 to 95% by weight of the fatty alcohol,2 to 25% by weight of the fatty oil and 2 to 25% by weight of the freefatty acid.
 9. An insect repellant according to claim 1, wherein thefatty acid alkyl ester is a methyl, ethyl or butyl ester of fatty acidsfrom natural or nature-identical vegetal or animal fatty oils selectedfrom the group consisting of rape-seed oil, sunflower oil, peanut oil,peanut butter, soy oil, safflower seed oil, cuphea oil, coconut oil,palm kernel oil, palm oil and fish oil.
 10. An insect repellantaccording to claim 1, wherein the alcohol is a natural fatty alcoholobtained from vegetal or animal oils, or fatty acids or fatty acid alkylesters obtained from said oils.
 11. An insect repellant according toclaim 1, wherein the nature-identical or synthetic fatty alcohols areobtained from paraffin or ethene.
 12. An insect repellant according toclaim 10, wherein the natural, nature-identical and synthetic fattyalcohols are saturated or have 1 to 3 unsaturated bonds per molecule.13. An insect repellant according to claim 4, wherein the fatty acidsare obtained by means of hydrolytic decomposition of natural ornature-identical vegetal or animal oils.
 14. An insect repellantaccording to claim 13, wherein the fatty acids have 6 to 19 carbon atomsin the chain.
 15. A method of repelling flying, biting and suckinginsects, which comprises applying to a human or beast a repellant amountof the insect repellant of claim
 1. 16. The method according to claim15, wherein the insect repellant is applied onto the skin of the humanor beast.